Organic semiconductor ink, photoelectric conversion layer, and organic photoelectric conversion element

Abstract

To provide an organic semiconductor ink for forming a photoelectric conversion layer, which enables formation of bridge structure in the photoelectric conversion layer by a blended additive agent and thereby enabling improvement of the heat resistance of the bridge structure, and thus, enables high versatility for selection of a semiconductor material and is easily applicable to a combination of existing p-type and n-type organic semiconductors.SOLUTION: An organic semiconductor ink is provided, containing a non-crosslinkable p-type organic semiconductor, a non-crosslinkable n-type organic semiconductor, a thermosetting component, and a solvent. Preferably, the thermosetting component includes epoxy resin as a main component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an organic semiconductor ink, a photoelectric conversion layer formed using this organic semiconductor ink, and an organic photoelectric conversion element having this photoelectric conversion layer. [Background technology]

[0002] Photoelectric conversion elements such as organic solar cells and organic photodetectors require heat resistance to withstand the heating environment that occurs during the reflow process during element manufacturing. However, these elements generally do not have sufficient heat resistance to withstand the heating environment expected during manufacturing, and this insufficient heat resistance may lead to a deterioration in photoelectric conversion characteristics. One of the reasons for the deterioration of the photoelectric conversion characteristics is thought to be as follows. Specifically, the phase-separated structure (compatibility between p-type and n-type organic semiconductors) of a bulk heterojunction (BHJ) photoelectric conversion layer consisting of p-type and n-type organic semiconductors plays an important role in determining photoelectric conversion characteristics. However, this phase-separated structure is not sufficiently stable against heat. Therefore, the phase-separated structure changes in high-temperature environments. This is because the p-type and n-type organic semiconductors in the photoelectric conversion layer flow under high-temperature conditions, causing partial aggregation between p-type and n-type organic semiconductors, which damages the bulk heterojunction between the p-type and n-type organic semiconductors. Therefore, various studies have been conducted to improve the heat resistance of the photoelectric conversion layer and the heat resistance stability of the phase-separated structure.

[0003] For example, Non-Patent Document 1 discloses that the heat resistance of a photoelectric conversion element can be improved by introducing a crosslinked structure into a photoelectric conversion layer using a p-type semiconductor into which a crosslinking group has been introduced. Non-patent document 2 describes the use of P3HT (poly(3-hexylthiophene)) and PC 61 BM([6,6]-phenyl-C 61It has been shown that the heat resistance of the photoelectric conversion layer can be improved by adding the thermally crosslinkable monomer OBOCO (octane-1,8-diylbis(1,4-dihydrobenzo[d][1,2]oxathiine-6-carboxylate-3-oxide)) to an active layer made of octane-1,8-diylbis(1,4-dihydrobenzo[d][1,2]oxathiine-6-carboxylate-3-oxide) and thermally curing the photoelectric conversion layer. Non-Patent Document 3 shows that the heat resistance of a photoelectric conversion layer made of PM6 and BTTT-2Cl is improved by adding an n-type semiconductor PZ1 to the photoelectric conversion layer, as described below.

[0004] [ka]

[0005] In Patent Document 1, a photoelectric conversion element that maintains good photoelectric conversion characteristics even after a heat resistance test at 150 to 220° C. for 50 minutes was successfully developed by using a predetermined semiconductor material. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Materials.Today.2015,18,425-435 [Non-patent document 2] J.Mater.Chem.A,2013,1,4589-4594 [Non-patent document 3] Nat.Commun.2020,11,1218 [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-057573 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the techniques of the above Non-Patent Documents 1 to 3 all have the following problems. The methods described in Non-Patent Documents 1 and 3 require the development of a new organic semiconductor having a crosslinking group. Furthermore, a fullerene derivative is essential for the curing reaction of the thermosetting monomer OBOCO in Non-Patent Document 2, and when this method is used, there are limitations on the selection of semiconductor materials for the photoelectric conversion layer. The method described in Patent Document 1 requires the use of a predetermined semiconductor material that is highly heat-resistant, and is therefore not very versatile in that there are limitations on the selection of semiconductor materials.

[0009] In view of these problems of the prior art, a general-purpose system that can impart heat resistance by post-addition of additives, etc., regardless of the semiconductor material selected, is ideal. Furthermore, when considering the imparting of heat resistance by stabilizing the phase-separated structure of the photoelectric conversion layer, a system that forms a crosslinked structure within the photoelectric conversion layer is effective. Furthermore, considering the impact on the semiconductor material responsible for photoelectric conversion, it is desirable that the curing reaction proceed with heat rather than light. However, the reality is that no technology that meets these requirements has been reported.

[0010] Therefore, an object of the present invention is to provide an organic semiconductor ink that can form a crosslinked structure in a photoelectric conversion layer by blending an additive therein, thereby improving the heat resistance of the photoelectric conversion layer, thereby allowing a high degree of freedom in the selection of semiconductor materials and allowing easy application to combinations of existing p-type organic semiconductors and n-type organic semiconductors; a photoelectric conversion layer using this organic semiconductor ink; and an organic photoelectric conversion element including this photoelectric conversion layer. [Means for solving the problem]

[0011] As a result of intensive research to solve the above problems, the inventors have found that by incorporating a thermosetting component capable of forming a crosslinked structure by itself into an organic semiconductor ink and then thermally curing the ink, the heat resistance of the formed photoelectric conversion layer can be improved, and that existing combinations of p-type organic semiconductors and n-type organic semiconductors can be used without the need for special functional design or molecular design.

[0012] The present invention was achieved based on these findings and has the following gist.

[0013] [1] An organic semiconductor ink comprising a non-crosslinkable p-type organic semiconductor, a non-crosslinkable n-type organic semiconductor, a thermosetting component, and a solvent.

[0014] [2] The organic semiconductor ink according to [1], wherein the thermosetting component contains an epoxy resin as a main component.

[0015] [3] The organic semiconductor ink according to [2], wherein the thermosetting component further contains a curing agent.

[0016] [4] The organic semiconductor ink according to [2] or [3], wherein the epoxy resin has an epoxy equivalent of 50 to 1000 g / eq.

[0017] [5] The organic semiconductor ink according to any one of [2] to [4], wherein the content of the epoxy resin in the thermosetting component is 38 to 100 mass %.

[0018] [6] The organic semiconductor ink according to any one of [1] to [5], wherein the curing temperature of the thermosetting component is within the range of 100 to 220°C.

[0019] [7] The organic semiconductor ink according to any one of [1] to [6], wherein the content of the thermosetting component is 1 to 100 parts by mass per 100 parts by mass of the total of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor.

[0020] [8] The organic semiconductor ink according to any one of [1] to [7], having a solids concentration of 10 to 30 mg / mL.

[0021] [9] The organic semiconductor ink according to any one of [1] to [8], wherein the solvent includes an aromatic solvent.

[0022]

[10] The organic semiconductor ink according to any one of [1] to [9], wherein the non-crosslinkable p-type organic semiconductor is a conjugated polymer, and the non-crosslinkable n-type organic semiconductor is a semiconductor not containing a fullerene skeleton.

[0023]

[11] The organic semiconductor ink according to

[10] , wherein the non-crosslinkable n-type organic semiconductor comprises a compound represented by the following formula (I) and / or a polymer of two or more compounds represented by the following formula (I):

[0024] [ka]

[0025] (In the above formula (I), A represents an atom selected from Group 14 of the periodic table, and X 1 ~X 4 R each independently represents a hydrogen atom or a halogen atom. 1a ,R 1b each independently represents a linear or branched alkyl group, R 2 ~R 5 each independently represents a linear or branched alkyl group, a linear or branched alkoxy group, a linear or branched thioalkyl group, or a hydrogen atom.

[0026]

[12] A photoelectric conversion layer obtained by heat-curing a coating of the organic semiconductor ink according to any one of [1] to

[11] .

[0027]

[13] An organic photoelectric conversion element comprising the photoelectric conversion layer according to

[12] . [Effects of the Invention]

[0028] The organic semiconductor ink of the present invention contains a thermosetting component, and by thermally curing this thermosetting component, a crosslinked structure can be formed in the photoelectric conversion layer. Therefore, the network of crosslinks in this crosslinked structure suppresses the flow of the p-type organic semiconductor and the n-type organic semiconductor in a high-temperature environment, and stabilizes the phase-separated structure of the p-type organic semiconductor and the n-type organic semiconductor, thereby improving heat resistance. As described above, in the present invention, the thermosetting component in the organic semiconductor ink itself can form a crosslinked structure, so there is no need to introduce functional groups for crosslinking reactions into the p-type organic semiconductor or n-type organic semiconductor, or to design the molecules for crosslinking reactions. Therefore, there is a high degree of freedom in the selection of semiconductor materials, and the present invention can be easily applied to combinations of existing p-type organic semiconductors and n-type organic semiconductors. Furthermore, the present invention can provide a photoelectric conversion layer with excellent heat resistance and little deterioration in photoelectric conversion properties even in high-temperature environments, as well as an organic photoelectric conversion element having this photoelectric conversion layer. [Brief explanation of the drawings]

[0029] [Figure 1] 1A and 1B are schematic diagrams illustrating the mechanism by which the heat resistance of a photoelectric conversion layer is improved by the organic semiconductor ink of the present invention, where (a) shows a conventional method and (b) shows the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of an embodiment of an organic photoelectric conversion element of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following describes in detail the form for carrying out the present invention, but the explanation of the constituent elements described below is a representative example of an embodiment of the present invention, and the present invention is not limited to these contents.

[0031] [Organic semiconductor ink] The organic semiconductor ink of the present invention is characterized by containing a non-crosslinkable p-type organic semiconductor, a non-crosslinkable n-type organic semiconductor, a thermosetting component, and a solvent.

[0032] In the present invention, the "non-crosslinkable" in "non-crosslinkable p-type organic semiconductor" means that the p-type organic semiconductor and the thermosetting component do not undergo a crosslinking reaction, and does not exclude crosslinking, polymerization, or condensation reactions between p-type organic semiconductors. Similarly, the "non-crosslinkable" in "non-crosslinkable n-type organic semiconductor" means that the n-type organic semiconductor and the thermosetting component do not undergo a crosslinking reaction, and does not exclude crosslinking, polymerization, or condensation reactions between n-type organic semiconductors. Furthermore, the "non-crosslinkable" of these organic semiconductors does not exclude crosslinking, polymerization, or condensation reactions between the "p-type organic semiconductor" and the "n-type organic semiconductor." Furthermore, the term "thermosetting component" refers to a component that itself crosslinks and hardens when exposed to heat to form a crosslinked structure.

[0033] <Mechanism> The mechanism by which the organic semiconductor ink of the present invention improves the heat resistance of the photoelectric conversion layer will be described with reference to FIG. As shown in Figure 1(a), conventional organic semiconductor inks consist of a p-type organic semiconductor (a p-type polymer in Figure 1) and an n-type organic semiconductor (an n-type molecule in Figure 1) dissolved in a solvent. The p-type polymer and n-type molecule are compatible with each other in the photoelectric conversion layer formed by depositing this organic semiconductor ink, resulting in high photoelectric conversion efficiency. However, with conventional methods, when exposed to a high-temperature environment (for example, a heat resistance test at 150 to 220°C for 50 minutes), the p-type polymer and n-type molecules flow and aggregate, significantly impairing their compatibility. This causes some of these molecules to become localized, resulting in a decrease in photoelectric conversion efficiency. In terms of heat resistance to prevent deterioration of photoelectric conversion characteristics due to the heating environment expected in the device manufacturing process, it is preferable that the heat resistance be 140°C or higher, more preferably 180°C or higher, and particularly preferably 200°C or higher.

[0034] In contrast, the organic semiconductor ink of the present invention contains a thermosetting component, and when this organic semiconductor ink is formed into a film and thermally cured, the thermosetting component forms a crosslinked structure in the formed photoelectric conversion layer. In a photoelectric conversion layer in which a crosslinked structure of the thermosetting component has been formed in this way, even when exposed to a high-temperature environment (for example, a heat resistance test at 150 to 220°C for 50 minutes), the flow of the p-type polymer and n-type molecules is prevented by the network of the crosslinked structure of the thermosetting component, and the compatibility between the two is hardly impaired, thereby suppressing a decrease in photoelectric conversion efficiency.

[0035] <Thermosetting component> The thermosetting component used in the present invention is not particularly limited as long as it can be cured by heating to form a network-like crosslinked structure in the photoelectric conversion layer.

[0036] From the viewpoint of facilitating the formation of a crosslinked structure effective for improving heat resistance, the thermosetting component is preferably one containing one or more of epoxy resin, phenol resin, melamine resin, urethane resin, silicone resin, etc. as the main component, and epoxy resin is particularly preferred. Note that the "main component" here refers to the component contained in the thermosetting component with the largest content, and the content of the main component in the thermosetting component is preferably 38% by mass or more, and particularly preferably 49 to 100% by mass.

[0037] When an epoxy resin is used as the thermosetting component, it is preferable to use a curing agent for the epoxy resin in combination, and by using a curing agent in combination, the thermosetting can proceed quickly.

[0038] (epoxy resin) The epoxy resin is not particularly limited, and any epoxy resin generally known as an epoxy resin can be used.

[0039] Usable epoxy resins include, for example, phenol novolac epoxy resins, orthocresol novolac epoxy resins, and epoxy resins having a triphenylmethane skeleton. Epoxidized novolak resins obtained by condensing or co-condensing phenols such as phenols including glycerin, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, etc. and / or naphthols such as α-naphthol, β-naphthol, dihydroxynaphthalene, etc. with compounds having an aldehyde group such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, salicylaldehyde, etc. under an acidic catalyst; diglycidyl ethers of bisphenol A, bisphenol F, bisphenol S, alkyl-substituted or unsubstituted biphenols, etc.; stilbene-type epoxy resins; hydroquinone-type epoxy resins; and polybasic acids such as phthalic acid and dimer acid. Examples of epoxy resins include glycidyl ester epoxy resins obtained by reacting epichlorohydrin with diaminodiphenylmethane, glycidylamine epoxy resins obtained by reacting epichlorohydrin with polyamines such as diaminodiphenylmethane or isocyanuric acid, epoxidized products of co-condensation resins of dicyclopentadiene and phenols, epoxy resins having a naphthalene ring, epoxidized products of aralkyl phenol resins such as phenol aralkyl resins and naphthol aralkyl resins containing a xylylene skeleton or a biphenylene skeleton, trimethylolpropane epoxy resins, terpene-modified epoxy resins, linear aliphatic epoxy resins or alicyclic epoxy resins obtained by oxidizing olefin bonds with a peracid such as peracetic acid, and sulfur-containing epoxy resins. These epoxy resins may be used alone or in combination of two or more.

[0040] Among these, novolac-type epoxy resins are preferred from the viewpoint of curability, dicyclopentadiene-type epoxy resins are preferred from the viewpoint of low moisture absorption, naphthalene-type epoxy resins and triphenylmethane-type epoxy resins are preferred from the viewpoint of heat resistance and low warpage, and biphenylene-type epoxy resins and naphthol aralkyl-type epoxy resins are preferred from the viewpoint of flame retardancy.

[0041] As the epoxy resin, it is preferable to use one with a small epoxy equivalent, since this easily forms a crosslinked structure in the photoelectric conversion layer that is effective in improving heat resistance by forming many crosslinking points in a network structure that can prevent the flow of p-type organic semiconductors and n-type organic semiconductors by heat curing, while it is preferable to use one with a large epoxy equivalent in terms of handleability.From this perspective, the epoxy equivalent of the epoxy resin is preferably 50 to 1000 g / eq, more preferably 70 to 500 g / eq, and particularly preferably 90 to 300 g / eq. In the present invention, the term "epoxy equivalent" is defined as "the mass of an epoxy compound containing one equivalent of an epoxy group" and can be measured in accordance with JIS K7236.

[0042] These epoxy resins can be commercially available products, and examples of commercially available epoxy resins that can be used include jER825 (epoxy equivalent weight 175 g / eq), jER827 (epoxy equivalent weight 185 g / eq), jER828 (epoxy equivalent weight 189 g / eq), jER834 (epoxy equivalent weight 250 g / eq), jER806 (epoxy equivalent weight 165 g / eq), jER807 (epoxy equivalent weight 170 g / eq), jER604 (epoxy equivalent weight 120 g / eq), jER630 (epoxy equivalent weight 98 g / eq), jER1032H60 (epoxy equivalent weight 169 g / eq), and q), jER152 (epoxy equivalent weight 175g / eq), jER154 (epoxy equivalent weight 178g / eq), jER157S70 (epoxy equivalent weight 210g / eq), YX-7700 (epoxy equivalent weight 273g / eq), YX-8000 (epoxy equivalent weight 205g / eq), YX-8800 (epoxy equivalent weight 179g / eq), YX-4000 (epoxy equivalent weight 186g / eq), YX-7105 (epoxy equivalent weight 480g / eq), YX-7400 (epoxy equivalent weight 440g / eq) (all trade names, manufactured by Mitsubishi Chemical Corporation), YD-127 (epoxy equivalent weight 18 5g / eq), YD-128 (epoxy equivalent weight 189g / eq), YDF-170 (epoxy equivalent weight 170g / eq), YDPN-638 (epoxy equivalent weight 180g / eq), TX-0911 (epoxy equivalent weight 172g / eq) (all trade names, manufactured by Nippon Steel & Sumikin Chemical & Material Co., Ltd.), EPICLON840 (epoxy equivalent weight 185g / eq), EPICLON850 (epoxy equivalent weight 189g / eq), EPICLON830 (epoxy equivalent weight 170g / eq), EPICLON835 (epoxy equivalent weight 172g / eq), HP-4032 (epoxy Equivalent weight 150g / eq), HP-4700 (epoxy equivalent weight 162g / eq), HP-4770 (epoxy equivalent weight 204g / eq), HP-4750 (epoxy equivalent weight 185g / eq), HP-7200 (epoxy equivalent weight 265g / eq), N-730A (epoxy equivalent weight 174g / eq), N-740 (epoxy equivalent weight 181g / eq), N-770 (epoxy equivalent weight 187g / eq), TSR-400 (epoxy equivalent weight 338g / eq) (all trade names, manufactured by DIC Corporation), GAN (epoxy equivalent weight 125g / eq), GOT (epoxy equivalent weight 135g / eq),Examples of epoxy equivalents include NC-2000 (epoxy equivalent weight 241 g / eq), NC-3000 (epoxy equivalent weight 275 g / eq) (all trade names, manufactured by Nippon Kayaku Co., Ltd.), MY-0500 (epoxy equivalent weight 110 g / eq), MY-0600 (epoxy equivalent weight 106 g / eq), ECN-1299 (epoxy equivalent weight 230 g / eq) (all trade names, manufactured by Huntsman Japan Co., Ltd.), DER331, DER354 (epoxy equivalent weight 170 g / eq) (epoxy equivalent weight 187 / eq), and DER332 (epoxy equivalent weight 173 g / eq) (all trade names, manufactured by The Dow Chemical Company), but are not limited to these.

[0043] The content of such epoxy resin in the thermosetting component is preferably 38 to 100 mass%, more preferably 49 to 99.5 mass%, and particularly preferably 75 to 99.5 mass%. If the content of the epoxy resin in the thermosetting component is equal to or greater than the above-mentioned lower limit, the epoxy resin can efficiently form a crosslinked structure that is effective in improving heat resistance. If the content of the epoxy resin in the thermosetting component is equal to or less than the above-mentioned upper limit, the content of the co-component components such as the curing agent shown below can be ensured, and the curing reaction can be smoothly promoted.

[0044] (hardening agent) In the present invention, a curing agent refers to a substance that contributes to the crosslinking reaction and / or chain extension reaction between epoxy groups in an epoxy resin. In the present invention, even substances that are usually called "curing accelerators" or "curing catalysts" are considered to be curing agents as long as they contribute to the crosslinking reaction and / or chain extension reaction between epoxy groups in an epoxy resin.

[0045] The curing agent is not particularly limited, and any commonly known epoxy resin curing agent can be used, including, for example, phenol-based curing agents, amine-based curing agents such as aliphatic amines, polyether amines, alicyclic amines, and aromatic amines, acid anhydride-based curing agents, amide-based curing agents, tertiary amines, and imidazoles.

[0046] Among these, it is preferable to use a phenol-based curing agent, an acid anhydride-based curing agent, or an amide-based curing agent from the viewpoint of heat resistance, etc. It is also preferable to use an imidazole compound from the viewpoint of sufficiently progressing the curing reaction and improving heat resistance. The curing agent may be used alone or in combination of two or more.

[0047] <Phenol-based hardener> Specific examples of phenolic curing agents include various polyhydric phenols such as bisphenol A, bisphenol F, bisphenol S, bisphenol AD, hydroquinone, resorcinol, methylresorcinol, biphenol, tetramethylbiphenol, dihydroxynaphthalene, dihydroxydiphenyl ether, thiodiphenols, phenol novolac resin, cresol novolac resin, phenol aralkyl resin, biphenyl aralkyl resin, naphthol aralkyl resin, terpene phenol resin, dicyclopentadiene phenol resin, bisphenol A novolac resin, trisphenolmethane type resin, naphthol novolac resin, brominated bisphenol A, and brominated phenol novolac resin. These include polyhydric phenol resins obtained by the condensation reaction of phenols and various aldehydes such as benzaldehyde, hydroxybenzaldehyde, crotonaldehyde, and glyoxal, polyhydric phenol resins obtained by the condensation reaction of xylene resin and phenols, co-condensation resins of heavy oils or pitches with phenols and formaldehydes, and various phenolic resins such as phenol-benzaldehyde-xylylene dimethoxide polycondensates, phenol-benzaldehyde-xylylene dihalide polycondensates, phenol-benzaldehyde-4,4'-dimethoxide biphenyl polycondensates, and phenol-benzaldehyde-4,4'-dihalide biphenyl polycondensates.

[0048] These phenolic curing agents may be used alone or in any combination of two or more in any blending ratio.

[0049] The amount of the phenolic curing agent added is preferably 0.1 to 1000 parts by mass, more preferably 500 parts by mass or less, even more preferably 300 parts by mass or less, and particularly preferably 100 parts by mass or less, per 100 parts by mass of the epoxy resin.

[0050] <Amine-based curing agent> Examples of amine-based curing agents (excluding tertiary amines) include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines.

[0051] Examples of aliphatic amines include ethylenediamine, 1,3-diaminopropane, 1,4-diaminopropane, hexamethylenediamine, 2,5-dimethylhexamethylenediamine, trimethylhexamethylenediamine, diethylenetriamine, iminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-hydroxyethylethylenediamine, and tetra(hydroxyethyl)ethylenediamine.

[0052] Examples of polyetheramines include triethylene glycol diamine, tetraethylene glycol diamine, diethylene glycol bis(propylamine), polyoxypropylene diamine, polyoxypropylene triamines, and the like.

[0053] Examples of alicyclic amines include isophoronediamine, methacenediamine, N-aminoethylpiperazine, bis(4-amino-3-methyldicyclohexyl)methane, bis(aminomethyl)cyclohexane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, and norbornenediamine.

[0054] Examples of aromatic amines include tetrachloro-p-xylylenediamine, m-xylylenediamine, p-xylylenediamine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, 2,4-diaminoanisole, 2,4-toluenediamine, 2,4-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diamino-1,2-diphenylethane, 2,4-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, m-aminophenol, m-aminobenzylamine, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, triethanolamine, methylbenzylamine, α-(m-aminophenyl)ethylamine, α-(p-aminophenyl)ethylamine, diaminodiethyldimethyldiphenylmethane, and α,α'-bis(4-aminophenyl)-p-diisopropylbenzene.

[0055] The amine-based curing agents listed above may be used alone or in any combination of two or more in any blending ratio.

[0056] The amine curing agent is preferably used so that the equivalent ratio of the functional groups in the curing agent to the epoxy groups in the epoxy resin is in the range of 0.8 to 1.5, since this range is preferable because unreacted epoxy groups and functional groups of the curing agent are less likely to remain.

[0057] Examples of tertiary amines include 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol.

[0058] The above-mentioned tertiary amines may be used alone or in any combination of two or more in any blending ratio.

[0059] The tertiary amine is preferably used so that the equivalent ratio of the functional groups in the curing agent to the epoxy groups in the epoxy resin is in the range of 0.8 to 1.5, since this range is preferable because it makes it difficult for unreacted epoxy groups or functional groups in the curing agent to remain.

[0060] <Acid anhydride curing agent> Examples of the acid anhydride curing agent include acid anhydrides and modified acid anhydrides. Examples of acid anhydrides include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, dodecenylsuccinic anhydride, polyadipic anhydride, polyazelaic anhydride, polysebacic anhydride, poly(ethyloctadecanedioic) anhydride, poly(phenylhexadecanedioic) anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhimic anhydride, trialkyltetrahydrophthalic anhydride, Examples of the dicarboxylic acid anhydride include methylcyclohexene dicarboxylic acid anhydride, methylcyclohexene tetracarboxylic acid anhydride, ethylene glycol bistrimellitate dianhydride, HET anhydride, Nadic anhydride, methylnadic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexane-1,2-dicarboxylic acid anhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride, and 1-methyl-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride.

[0061] Examples of modified acid anhydrides include those obtained by modifying the above-mentioned acid anhydrides with glycols. Examples of glycols that can be used for modification include alkylene glycols such as ethylene glycol, propylene glycol, and neopentyl glycol, and polyether glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. Furthermore, copolymer polyether glycols of two or more of these glycols and / or polyether glycols can also be used.

[0062] In the case of modified acid anhydrides, it is preferable to modify the acid anhydride with 0.4 mol or less of glycol per mol of acid anhydride. When the modification amount is not more than the above upper limit, the viscosity of the epoxy resin composition does not become too high, and workability tends to be improved, and the rate of the curing reaction with the epoxy resin also tends to be improved.

[0063] The acid anhydride curing agents listed above may be used alone or in any combination of two or more in any amount.

[0064] When an acid anhydride curing agent is used, it is preferable to use it so that the equivalent ratio of the functional groups in the curing agent to the epoxy groups in the epoxy resin is in the range of 0.8 to 1.5, since it is preferable if it is within this range because unreacted epoxy groups and functional groups of the curing agent are less likely to remain.

[0065] <Amide-based curing agent> Examples of the amide-based curing agent include dicyandiamide and its derivatives, polyamide resins, and the like. The amide curing agent may be used alone or as a mixture of two or more kinds in any combination and ratio. When an amide curing agent is used, it is preferable to use the amide curing agent in an amount of 0.1 to 20 mass % based on the total amount of the epoxy resin and the amide curing agent.

[0066] <Imidazoles> Examples of imidazoles include 2-phenylimidazole, 2-ethyl-4(5)-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl- Examples of such imidazoles include 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and adducts of epoxy resins with the above imidazoles. Note that, since imidazoles have catalytic activity, they can generally be classified as curing accelerators, but in the present invention they are classified as curing agents.

[0067] The imidazoles listed above may be used alone or in any combination and ratio of two or more.

[0068] When an imidazole is used, it is preferable to use the imidazole in an amount of 0.1 to 20% by mass based on the total amount of the epoxy resin and the imidazole.

[0069] (curing accelerator) The thermosetting component according to the present invention may contain a curing accelerator, which can shorten the curing time and lower the curing temperature. The curing accelerator is not particularly limited, but specific examples include organic phosphines, phosphorus compounds such as phosphonium salts, tetraphenylboron salts, organic acid dihydrazides, boron halide amine complexes, and the like.

[0070] Phosphorus compounds that can be used as curing accelerators include triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkylalkoxyphenyl)phosphine, tris(dialkylphenyl)phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, tris(tetraalkoxyphenyl)phosphine, trialkylphosphine, Examples of such phosphines include organic phosphines such as phosphine, dialkylarylphosphine, and alkyldiarylphosphine; complexes of these organic phosphines with organic borons; and compounds obtained by adding these organic phosphines to quinone compounds such as maleic anhydride, 1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, and phenyl-1,4-benzoquinone; and compounds such as diazophenylmethane.

[0071] Among the curing accelerators listed above, organic phosphines and phosphonium salts are preferred, and organic phosphines are most preferred. The curing accelerator may be one of the above-mentioned ones, or two or more of them may be mixed in any combination and ratio.

[0072] The curing accelerator is preferably used in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the epoxy resin. It is more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, while it is more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. When the content of the curing accelerator is equal to or greater than the lower limit, a good curing acceleration effect can be obtained, while when the content is equal to or less than the upper limit, the desired cured physical properties can be easily obtained, which is preferred.

[0073] (curing temperature) The thermosetting component used in the present invention preferably has a curing temperature within the range of 100 to 220°C. A curing temperature of 100°C or higher can prevent the thermosetting component from reacting in the ink during preparation of the organic semiconductor ink. When forming a crosslinked structure by curing the thermosetting component in the photoelectric conversion layer through heating, a higher curing temperature is preferable. On the other hand, a curing temperature of 220°C or lower can prevent excessively high heating during the formation of the photoelectric conversion layer, which can cause the p-type organic semiconductor and n-type organic semiconductor to flow before the crosslinked structure is formed through curing, resulting in a change in the phase separation structure and a decrease in photoelectric conversion characteristics. From this viewpoint, the curing temperature of the thermosetting component is more preferably 120 to 220°C, and particularly preferably 140 to 220°C.

[0074] In order to set the curing temperature of the thermosetting component within the above range, techniques such as selecting an epoxy resin having an appropriate curing temperature and selecting an appropriate curing agent and curing accelerator and adjusting the blending ratios thereof may be adopted.

[0075] (Thermosetting component content) The content of the thermosetting component in the organic semiconductor ink of the present invention is preferably 1 to 100 parts by mass, more preferably 1 to 40 parts by mass, and particularly preferably 1 to 10 parts by mass, per 100 parts by mass of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor combined. Furthermore, when an epoxy resin is used as the thermosetting component, the content of the epoxy resin in the organic semiconductor ink of the present invention is preferably 1 to 100 parts by mass, more preferably 1 to 40 parts by mass, and particularly preferably 1 to 10 parts by mass, per 100 parts by mass of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor combined.

[0076] When the content ratio of the thermosetting component and the epoxy resin in the organic semiconductor ink is equal to or greater than the above-mentioned lower limit, a crosslinked structure effective for improving heat resistance can be formed in a sufficient proportion in the photoelectric conversion layer. When the content ratio of the thermosetting component in the organic semiconductor ink is equal to or less than the above-mentioned upper limit, the content of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor can be ensured, and a photoelectric conversion layer with excellent photoelectric conversion efficiency can be formed.

[0077] <Non-crosslinkable p-type organic semiconductor> The non-crosslinkable p-type organic semiconductor is not particularly limited and may be any known compound, but is preferably a donor semiconductor, typically an organic semiconductor (compound). For example, a hole-transporting organic compound that is a p-type conjugated polymer may be mentioned, and a compound that has the property of readily donating electrons may be used. Specific examples of skeletons having excellent hole transport properties include a carbazole structure, a thiophene structure, a benzodithiophene structure, a thienothiophene structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure, and a pyrene structure. Among these, it is particularly preferable to use a material that can be mixed with a non-crosslinkable n-type organic semiconductor described below to form a film by coating.

[0078] Specifically, for example, the one represented by the following formula (II) is used: In formula (II), n is a positive number.

[0079] [ka]

[0080] In order to improve the properties of the non-crosslinkable p-type organic semiconductor used in the present invention as a p-type semiconductor, the weight-average molecular weight is preferably 100,000 or more, more preferably 150,000 or more. From the viewpoint of solubility in solvents, the upper limit is preferably 400,000 or less, more preferably 300,000 or less. Here, the weight average molecular weight of the non-crosslinkable p-type organic semiconductor is a value determined by size exclusion chromatography.

[0081] <Non-crosslinkable n-type organic semiconductor> An n-type semiconductor is an acceptor semiconductor, and is mainly represented by an electron transport compound, which refers to a compound that has the property of readily accepting electrons. More specifically, when two compounds are used in contact, it refers to the compound with the greater electron affinity. Therefore, any compound with electron-accepting properties can be used as an acceptor compound. For example, fused aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), 5- to 7-membered heterocyclic compounds containing a nitrogen atom, an oxygen atom, or a sulfur atom (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazoline, Examples of suitable metal complexes include those having, as a ligand, a benzoindene, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyrazine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), a polyarylene compound, a fluorene compound, a cyclopentadiene compound, a silyl compound, or a nitrogen-containing heterocyclic compound. However, as described above, any compound having a larger electron affinity than the compound used as the donor semiconductor may be used as the acceptor semiconductor.

[0082] When a fullerene skeleton is used as an n-type semiconductor, even if a bulk heterojunction structure is used to increase photoelectric conversion efficiency, the presence of the bulky fullerene skeleton increases the distance between the n-type semiconductor and the p-type semiconductor, resulting in a decrease in photoelectric conversion efficiency.

[0083] Therefore, in the non-crosslinkable p-type organic semiconductor of the present invention, the ratio of the n-type semiconductor having a fullerene skeleton to the n-type semiconductor not having a fullerene skeleton is preferably 10 mass % or less, and more preferably the n-type semiconductor is a fullerene skeleton-free semiconductor in which substantially no n-type semiconductor having a fullerene skeleton is contained. Here, "substantially free of a fullerene skeleton" means that the non-fullerene n-type semiconductor is responsible for transporting electrons among the charges generated in the photoelectric conversion layer, and a small amount may be contained to improve the morphology of the photoelectric conversion layer. For such a purpose, the n-type semiconductor containing a fullerene skeleton is usually contained in an amount of 5% by mass or less, and preferably 2% by mass or less, of the non-fullerene n-type semiconductor not having a fullerene skeleton.

[0084] The non-crosslinkable n-type organic semiconductor used in the present invention preferably contains a compound represented by the following formula (I) and / or a polymer of two or more compounds represented by the following formula (I), particularly from the viewpoints of compatibility with the non-crosslinkable p-type organic semiconductor and the ability to form a (BHJ) type photoelectric conversion layer.

[0085] [ka]

[0086] (In the above formula (I), A represents an atom selected from Group 14 of the periodic table, and X 1 ~X 4 R each independently represents a hydrogen atom or a halogen atom. 1a ,R 1b each independently represents a linear or branched alkyl group, R 2 ~R 5 each independently represents a linear or branched alkyl group, a linear or branched alkoxy group, a linear or branched thioalkyl group, or a hydrogen atom.

[0087] In the above formula (I), A is preferably a carbon atom or a silicon atom. X 1 ~X 4are each independently a hydrogen atom or a halogen atom, and the halogen atom is preferably a fluorine atom or a chlorine atom. R 1a ,R 1b are each independently a straight-chain or branched alkyl group, and the alkyl group preferably has 8 to 24 carbon atoms, particularly 10 to 20 carbon atoms, and especially 12 to 18 carbon atoms.

[0088] Examples of the linear or branched alkyl group having 8 to 24 carbon atoms include linear alkyl groups such as n-octyl, n-decyl, lauryl, myristyl, palmityl, and stearyl groups; branched primary alkyl groups such as 2-ethylhexyl and 2-butyloctyl groups; and secondary alkyl groups such as 2-octyl, 2-nonyl, and 2-decyl groups. Of these, linear alkyl groups or branched primary alkyl groups are preferred, with 2-ethylhexyl or 2-butyloctyl being particularly preferred.

[0089] R 2 ~R 5 are each independently a linear or branched alkyl group, a linear or branched alkoxy group, a linear or branched thioalkyl group, or a hydrogen atom, and the alkyl group, alkoxy group, or thioalkyl group preferably has 8 to 24 carbon atoms, particularly 10 to 20 carbon atoms, and particularly 12 to 18 carbon atoms. R 2 ~R 5 is preferably each independently an alkoxy group having 8 to 24 carbon atoms, and specific examples thereof include a 2-ethylhexyloxy group or a palmityloxy group.

[0090] From the viewpoint of compatibility with non-crosslinkable p-type organic semiconductors and ability to form BHJ-type photoelectric conversion layers, 1a and R 1b are preferably the same group, and R 2 ~R 5 is preferably composed of two or more different groups.

[0091] <Content ratio of non-crosslinkable p-type organic semiconductor and non-crosslinkable n-type organic semiconductor> The ratio of the non-crosslinkable p-type organic semiconductor to the non-crosslinkable n-type organic semiconductor contained in the organic semiconductor ink of the present invention is preferably 0.5 to 2.5 times, particularly 1.0 to 2.0 times, in terms of the mass ratio of the non-crosslinkable n-type organic semiconductor to the non-crosslinkable p-type organic semiconductor (n-type organic semiconductor / p-type organic semiconductor mass ratio). If the amount of non-crosslinkable n-type organic semiconductor is higher than the above range and the amount of non-crosslinkable p-type organic semiconductor is lower than the above range, sensitivity in the near-infrared region tends to decrease. Conversely, if the amount of non-crosslinkable p-type organic semiconductor is higher than the above range and the amount of non-crosslinkable n-type organic semiconductor is lower than the above range, dark current tends to be more likely to occur.

[0092] <Solvent> The solvent contained in the organic semiconductor ink of the present invention may be any solvent capable of dissolving the non-crosslinkable p-type organic semiconductor, the non-crosslinkable n-type organic semiconductor, and the thermosetting component, and examples thereof include aromatic hydrocarbon solvents such as toluene, xylene, mesitylene, and cyclohexylbenzene, aromatic halogen-containing solvents such as chlorobenzene and o-dichlorobenzene, aliphatic halogen-containing solvents such as 1,2-dichloroethane, and aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA). ether-based solvents such as aromatic ethers such as methyl ether, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole; aliphatic ester-based solvents such as ethyl acetate, n-butyl acetate, ethyl lactate, and n-butyl lactate; and ester-based solvents such as aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, isopropyl benzoate, propyl benzoate, and n-butyl benzoate. These may be used alone or in combination of two or more.

[0093] Among these solvents, aromatic solvents are preferred from the viewpoint of the solubility of the non-crosslinked p-type organic semiconductor and the non-crosslinked p-type organic semiconductor, and aromatic halogen-containing solvents are particularly preferred.

[0094] <Other ingredients> The organic semiconductor ink of the present invention may contain, in addition to the above-mentioned thermosetting component, non-crosslinkable p-type organic semiconductor, non-crosslinkable n-type organic semiconductor and solvent, a stabilizer, a thickener, etc., as necessary. However, when the organic semiconductor ink of the present invention contains these other components, in order to fully obtain the inherent effects of the organic semiconductor ink, it is preferable that the content of the other components in the organic semiconductor ink is 10 mass % or less relative to the total of the thermosetting component, non-crosslinkable p-type organic semiconductor, non-crosslinkable n-type organic semiconductor, and other components.

[0095] <Solid content concentration> The solids concentration of the organic semiconductor ink of the present invention, i.e., the total content of the thermosetting component, non-crosslinkable p-type organic semiconductor, non-crosslinkable n-type organic semiconductor, and other components contained as needed, excluding the solvent in the organic semiconductor ink, is preferably 10 to 30 mg / mL, and more preferably 12 to 24 mg / mL. If the solids concentration of the organic semiconductor ink is equal to or higher than the lower limit, the efficiency of forming the photoelectric conversion layer is excellent, while if it is equal to or lower than the upper limit, the organic semiconductor ink can be easily prepared and is easy to handle.

[0096] <Method of manufacturing organic semiconductor ink> The organic semiconductor ink of the present invention can be produced by adding and mixing the above-mentioned thermosetting component, non-crosslinkable p-type organic semiconductor, non-crosslinkable n-type organic semiconductor, and other components, if necessary, to a solvent so as to achieve a predetermined concentration. In this case, there is no particular restriction on the order in which the components are added.

[0097] <Applications of organic semiconductor ink> The organic semiconductor ink of the present invention contains a thermosetting component, and thus can form a photoelectric conversion layer with excellent heat resistance, and can be effectively used to form a photoelectric conversion layer of an organic photoelectric conversion element.

[0098] [Photoelectric conversion layer] The photoelectric conversion layer of the present invention is formed by heat-curing a coating of the organic semiconductor ink of the present invention.

[0099] The photoelectric conversion layer of the present invention can be produced by forming a film of the organic semiconductor ink of the present invention by a wet film formation method on a surface on which the photoelectric conversion layer is to be formed (usually on the electrode surface of the organic photoelectric conversion element of the present invention described below, or on another layer such as a hole transport layer formed on the electrode), and then heat-curing the formed coating film.

[0100] The wet film-forming method is not particularly limited, but specific examples include spin coating. In this case, the spin coating conditions may be appropriately determined according to a standard method, taking into account the viscosity of the organic semiconductor ink, etc. The temperature during film formation is also not particularly limited, but is a temperature at which the thermosetting component does not harden, and is usually 100°C or less, for example, about 20 to 80°C.

[0101] The heating conditions for heat-curing the formed coating film are those at which the thermosetting component can cure to form a crosslinked structure, and although these vary depending on the type of thermosetting component, the aforementioned preferred curing temperature conditions, i.e., 100 to 220°C, more preferably 120 to 220°C, and particularly preferably 140 to 220°C, are preferred. The heating time may also be long enough to cure the thermosetting component and form a crosslinked structure, and although it varies depending on the type of thermosetting component and the heating temperature, it is usually about 1 to 60 minutes.

[0102] The thickness of the photoelectric conversion layer of the present invention thus formed can be arbitrarily designed depending on the configuration of the photoelectric conversion layer and the use of the organic photoelectric conversion element, but if it is too thin, light absorption will be insufficient and efficiency will decrease, and if it is too thick, internal resistance will increase and loss will become large, so it is usually about 10 nm to 1 μm.

[0103] [Organic photoelectric conversion element] The organic photoelectric conversion element of the present invention has the above-described photoelectric conversion layer of the present invention.

[0104] The structure of the organic photoelectric conversion element of the present invention can be, for example, as described in JP-A-2007-324587, and is not particularly limited. For example, the organic photoelectric conversion element may have a structure in which a transparent electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and a metal electrode are laminated in this order on a transparent substrate, or may have a structure in which a transparent electrode, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a metal electrode are laminated in this order on a transparent substrate.

[0105] 1 is a schematic cross-sectional view showing an example of an organic photoelectric conversion element of the present invention. This organic photoelectric conversion element 10 has a first electrode 11, a hole transport layer 12, a photoelectric conversion layer 13, an electron transport layer 14, and a second electrode 15 as a lower electrode laminated in this order. The hole transport layer 12, the photoelectric conversion layer 13, and the electron transport layer 14 form an organic photoelectric film 20. Typically, a substrate is provided on the side of the first electrode 11 opposite the hole transport layer 12.

[0106] <Substrate> The organic photoelectric conversion element may include a substrate for supporting the first electrode, the hole transport layer, the photoelectric conversion layer, the electron transport layer, the second electrode, etc. The substrate may be provided on either the first electrode side or the second electrode side, or on both sides, but is preferably provided at least on the first electrode side. The substrate can be made of any material, but if light is incident from the substrate side, it must be made of a highly transparent material.

[0107] Examples of materials constituting the substrate include inorganic materials such as glass, sapphire, and titania; organic materials such as polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, fluororesin, vinyl chloride, polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, and polynorbornene; paper materials such as paper and synthetic paper; and composite materials such as metals such as stainless steel, titanium, and aluminum whose surfaces are coated or laminated to impart insulating properties. The substrate may be made of one material alone, or two or more materials may be used in any combination and ratio.

[0108] Furthermore, there is no limitation on the shape and dimensions of the substrate, and they can be set arbitrarily. Furthermore, another layer may be laminated on the substrate in order to impart gas barrier properties or control the surface condition.

[0109] The thickness of the substrate can be designed arbitrarily depending on the application, constituent materials, etc. of the organic photoelectric conversion element. However, if it is too thin, it will lack strength and will not function as a support member, and if it is too thick, costs will increase. Therefore, the substrate is usually in the form of a film or plate having a thickness of about 10 μm to 50 mm.

[0110] <Electrode> The electrodes (first electrode, second electrode) can be made of any conductive material.

[0111] Examples of materials for electrodes include metals such as platinum, gold, silver, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium, and sodium, or alloys thereof; metal oxides such as indium oxide and tin oxide, or composite oxides thereof (e.g., ITO and IZO); conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyacetylene; conductive polymers to which dopants such as acids such as hydrochloric acid, sulfuric acid, and sulfonic acid, Lewis acids such as FeCl3, halogen atoms such as iodine, and metal atoms such as sodium and potassium have been added; and conductive composite materials in which conductive particles such as metal particles, carbon black, fullerenes, and carbon nanotubes are dispersed in a matrix such as a polymer binder. The electrode materials may be used singly or in any combination and ratio of two or more.

[0112] In an organic photoelectric conversion element, at least one pair (two electrodes) of electrodes is provided, and a photoelectric conversion layer is provided between the pair of electrodes. In this case, it is preferable that at least one of the pair of electrodes is transparent (i.e., it transmits light absorbed by the photoelectric conversion layer for power generation). Examples of materials for the transparent electrode include composite oxides such as indium tin oxide (ITO) and indium zinc oxide (IZO); metal thin films, etc. In this case, there is no specific limit to the range of light transmittance, but considering the photoelectric conversion efficiency of the organic photoelectric conversion element, it is preferably 80% or more. Note that the light transmittance can be measured using a conventional spectrophotometer.

[0113] The electrode has the function of collecting holes and electrons generated in the photoelectric conversion layer. Therefore, it is preferable to use, as the constituent material of the electrode, a constituent material suitable for collecting holes and electrons from among the above-mentioned materials. Examples of electrode materials suitable for collecting holes include materials with a high work function such as Au and ITO. On the other hand, examples of electrode materials suitable for collecting electrons include materials with a low work function such as Al.

[0114] There is no particular limitation on the thickness of the electrode, and it is determined appropriately taking into consideration the material used and the required conductivity, transparency, etc., but it is usually about 10 nm to 100 μm.

[0115] There are no limitations on the method for forming the electrodes, and they can be formed by dry processes such as vacuum deposition and sputtering. They can also be formed by wet processes using conductive ink, for example. Any conductive ink can be used, including conductive polymers and metal particle dispersions. The electrodes can be stacked in two or more layers, and can be surface-treated to improve their properties (electrical properties, wetting properties, etc.).

[0116] <Hole transport layer> Known hole transport materials can be used for the hole transport layer. Specific examples of hole transport polymers that can be used include polytriarylamine compounds, such as those exemplified below. Other examples include 2,7-bis(4-bromophenyl)-9,9-dihexylfluorene, 2-amino-9,9-dihexylfluorene, and polytolylarylamine compounds synthesized from 4-(4-(1,1-bis(4'-bromo-[1,1'-biphenyl]-4-yl)ethyl)phenyl)-1,2-dihydrocyclobuta[a]naphthalene, as described in JP-A-2019-173032, 4,4'-dibromobiphenyl, and 2-amino-9 Polytriarylamine compounds synthesized from 4,4'-dibromobiphenyl, 4-(3,5-dibromophenyl)-1,2-dihydrocyclobuta[a]naphthalene, and 2-amino-9,9-dihexylfluorene can be used, but are not limited to these.

[0117] [ka]

[0118] [ka]

[0119] [ka]

[0120] The method for forming the hole transport layer is not particularly limited, but it is preferably formed by a wet film formation method using a hole transporting polymer. To form the hole transport layer by the wet film formation method, a composition for forming the hole transport layer containing a hole transporting polymer and a solvent is used.

[0121] The solvent is sufficient as long as it can dissolve the hole-transporting polymer, and is usually a solvent that can dissolve the hole-transporting polymer at room temperature in an amount of 0.05% by mass or more, preferably 0.5% by mass or more, and more preferably 1% by mass or more. The solvent is not particularly limited, but preferred examples include ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and amide-based solvents.

[0122] Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA), and aromatic ethers such as 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole.

[0123] Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Examples of aromatic hydrocarbon solvents include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, etc. In addition to these, dimethyl sulfoxide, etc. can also be used.

[0124] The concentration of the hole transport polymer in the composition for forming a hole transport layer is arbitrary as long as it does not significantly impair the effects of the present invention, and a lower concentration is preferable in terms of uniformity of film thickness, while a higher concentration is preferable in terms of preventing defects from occurring in the hole transport layer. Specifically, the concentration is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and particularly preferably 0.5% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0125] The concentration of the solvent in the composition for forming a hole transport layer is usually 10% by mass or more, preferably 30% by mass or more, and more preferably 50% by mass or more.

[0126] When forming a hole transport layer using a composition for forming a hole transport layer, the composition is usually heated after application. The heating method is not particularly limited, but in the case of heat drying, the layer formed using the composition for forming a hole transport layer is usually heated to 100°C or higher, preferably 120°C or higher, more preferably 150°C or higher, and usually 400°C or lower, preferably 350°C or lower, more preferably 300°C or lower. The heating time is usually 1 minute or more, preferably 24 hours or less. The heating method is not particularly limited, but may be, for example, placing the laminate having the formed layer on a hot plate or heating in an oven. For example, heating conditions such as heating on a hot plate at 120°C or higher for 1 minute or more may be used.

[0127] The thickness of the hole transport layer is in one embodiment 50 nm or more and 100 nm or less, and in another embodiment, more than 100 nm and 400 nm or less, preferably 350 nm or less, that is, 50 nm or more and 400 nm or less, preferably 350 nm or less. When the thickness of the hole transport layer is equal to or greater than the lower limit, the dark current reduction effect due to the hole transport layer being provided as a blocking layer can be effectively obtained. When the thickness of the hole transport layer is equal to or less than the upper limit, the angle of incidence of light can be widened in a CMOS image sensor using an organic photoelectric conversion element, and the organic photoelectric conversion element can be made thinner.

[0128] To effectively reduce dark current, the hole transport layer preferably has a LUMO shallower than the n-type organic semiconductor of the photoelectric conversion layer by 0.3 eV or more, more preferably by 0.5 eV or more, and even more preferably by 1.0 eV or more. Furthermore, because the hole transport layer plays a role in efficiently transporting holes generated in the photoelectric conversion layer to the first electrode, the difference in HOMO with the p-type organic semiconductor of the photoelectric conversion layer is preferably within 0.5 eV, and more preferably within 0.3 eV.

[0129] <Photoelectric conversion layer> The photoelectric conversion layer is a layer that absorbs light and separates charges, and the photoelectric conversion layer of the organic photoelectric conversion element of the present invention is the photoelectric conversion layer of the present invention described above, formed from the organic semiconductor ink of the present invention described above.

[0130] <Electron transport layer> Although an electron transport layer is not necessarily required for an organic photoelectric conversion element, providing an electron transport layer between the photoelectric conversion layer and the second electrode can improve the photoelectric conversion efficiency and reduce the dark current.

[0131] The electron transport layer is formed from a compound capable of efficiently transporting electrons generated in the photoelectric conversion layer to the second electrode. The electron transporting compound used in the electron transport layer must have high electron injection efficiency from the photoelectric conversion layer and high electron mobility, allowing it to efficiently transport the injected electrons. For this reason, the difference in LUMO between the electron transport layer and the n-type semiconductor of the photoelectric conversion layer is preferably 1.5 eV or less, and more preferably 1.0 eV. Furthermore, when dark current is reduced by the electron transport layer, the electron transport layer preferably has a HOMO that is 0.3 eV or more deeper than the p-type semiconductor of the photoelectric conversion layer, preferably 0.5 eV or more deeper, and more preferably 1.0 eV or more deeper.

[0132] Examples of electron transporting compounds used in the electron transport layer include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo[h]quinoline, oxadiazole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (U.S. Pat. No. 5,645,948), quinoxaline compounds (Japanese Patent Laid-Open No. 6-207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

[0133] Furthermore, metal oxides such as titanium oxide, zinc oxide, tin oxide, and cerium oxide can also be used as materials for forming the electron transport layer. In this case, the electron transport layer can be formed by wet-forming nanoparticles of the metal oxide and drying them to form a metal oxide layer, or by wet-forming a precursor and then converting it by heating.

[0134] The thickness of the electron transport layer is usually 1 nm or more, preferably 5 nm or more, and on the other hand, is usually 300 nm or less, preferably 100 nm or less.

[0135] The electron transport layer can be formed by a wet film-forming method or a vacuum deposition method, but the vacuum deposition method is usually used.

[0136] <Other constituent layers> The organic photoelectric conversion element may include constituent layers other than the substrate, first and second electrodes, hole transport layer, photoelectric conversion layer, and electron transport layer as long as the effects of the present invention are not significantly impaired. For example, the organic photoelectric conversion element may be provided with a protective film covering the photoelectric conversion layer portion and even the electrode portion in order to minimize the influence of the outside air. The protective layer may be composed of, for example, a polymer film such as a styrene resin, an epoxy resin, an acrylic resin, a polyurethane, a polyimide, a polyvinyl alcohol, a polyvinylidene fluoride, or a polyethylene-polyvinyl alcohol copolymer; an inorganic oxide film or nitride film such as silicon oxide, silicon nitride, or aluminum oxide; or a laminate film thereof.

[0137] There are no limitations on the method for forming the protective film. For example, when the protective film is a polymer film, examples include a formation method by coating and drying a polymer solution, and a formation method by coating or vapor-depositing a monomer and polymerizing it. When forming a polymer film, it is also possible to further perform a crosslinking process or form a multilayer film. On the other hand, when the protective film is an inorganic film such as an inorganic oxide film or a nitride film, it is possible to use a formation method using a vacuum process such as a sputtering method or a vapor deposition method, or a formation method using a solution process such as a sol-gel method.

[0138] In addition, in order to allow the electrode to efficiently collect the charges generated in the photoelectric conversion layer, a charge injection layer may be provided between the first electrode and the hole transport layer or between the electron transport layer and the second electrode. Furthermore, the organic photoelectric conversion element may be provided with an optical filter that blocks ultraviolet light, for example, on the light incident side. Since ultraviolet light generally accelerates the deterioration of organic photoelectric conversion elements, blocking this ultraviolet light can extend the life of the organic photoelectric conversion element.

[0139] <Method of manufacturing organic photoelectric conversion element> An organic photoelectric conversion element is usually produced by laminating a first electrode, a hole transport layer, a photoelectric conversion layer, and a second electrode on a substrate in this order using the methods described above, with a step of forming an electron transport layer or the like between these layers as needed.

[0140] <Applications of organic photoelectric conversion elements> The photoelectric conversion element of this embodiment is used in an optical sensor, an image sensor, etc. In this case, the optical sensor and the image sensor may have known configurations. [Example]

[0141] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the following examples.

[0142] <Measurement method> -Method of measuring film thickness The film thickness can be measured using a contact type, such as a stylus surface profile evaluation device Dektak150 (manufactured by ULVAC), or a non-contact type, such as a profile measurement laser microscope VK-X200 (manufactured by Keyence Corporation). External quantum efficiency measurement method: The spectral sensitivity was measured using a solar simulator and electrical property measuring device (manufactured by Bunkoukeiki Co., Ltd.), and the external quantum efficiency was obtained when a voltage of -5 V was applied to the element in light with a wavelength of 940 nm.

[0143] Example 1 A transparent conductive film of indium tin oxide (ITO) was patterned on a glass substrate as an electrode. The surface of the ITO substrate was treated with an ultraviolet ozone cleaner (NL-UV253, manufactured by Nippon Laser Electronics Co., Ltd.) for 10 minutes, and then a hole transport layer was formed as follows.

[0144] A composition for forming a hole transport layer was prepared by dissolving 60 mg of a polytriarylamine compound (hole transport polymer) represented by the following formula (1) in 1 mL of anisole. This composition was spin-coated on the electrode surface of an ITO substrate at 1000 rpm for 60 seconds, and then dried by heating at 240°C for 30 minutes to form a hole transport layer with a thickness of 300 nm.

[0145] [ka]

[0146] The following materials were used: a non-crosslinkable p-type organic semiconductor, a non-crosslinkable n-type organic semiconductor, and an epoxy resin. The organic semiconductor ink was prepared by dissolving the resin and the curing agent. Non-crosslinkable p-type organic semiconductor: p-type organic semiconductor represented by the above formula (II) (weight average molecular weight: 240,000) Non-crosslinkable n-type organic semiconductor: In the above formula (I), A = carbon atom X 1 ~X 4 = chlorine atom R 1a ,R 1b = 2-ethylhexyl group R 2 = 2-ethylhexyl group R 3 = 2-ethylhexyloxy group R 4 ,R 5 = hydrogen atoms n-type organic semiconductor compound Epoxy resin :workman epoxy resin (Mitsubishi Chemical Corporation) jER828 (epoxy equivalent weight 189g / eq)

[0148] Hardener: 2-ethyl-4-methylimidazole Solvent: Chlorobenzene

[0149] The mass ratio of the non-crosslinkable p-type organic semiconductor to the non-crosslinkable n-type organic semiconductor in the organic semiconductor ink (n-type organic semiconductor / p-type organic semiconductor) was 1.2, the content of the thermosetting component relative to a total of 100 parts by mass of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor was 5.25 parts by mass (epoxy resin content: 5 parts by mass, curing agent content: 0.25 parts by mass), and the solids concentration of the organic semiconductor ink was 16.5 mg / mL.

[0150] This organic semiconductor ink was spin-coated onto the hole transport layer at 1000 revolutions per minute, and then heated at 120°C for 30 minutes to harden the epoxy resin, forming a photoelectric conversion layer with a thickness of 150 nm.

[0151] Next, a 40 nm thick film of C60 fullerene (manufactured by Frontier Carbon Co., Ltd.) as an electron transport material and a 100 nm thick film of aluminum as a metal electrode were formed in vacuum to obtain an organic photoelectric conversion element.

[0152] <Example 2> An organic photoelectric conversion element was produced in the same manner as in Example 1, except that the heating temperature for heat curing during the formation of the photoelectric conversion layer was set to 160°C.

[0153] Example 3 An organic photoelectric conversion element was produced in the same manner as in Example 1, except that the heating temperature for heat curing during the formation of the photoelectric conversion layer was set to 200°C.

[0154] <Reference example 1> An organic photoelectric conversion element was produced in the same manner as in Example 1, except that heat curing was not carried out when the photoelectric conversion layer was formed.

[0155] <Heat resistance test> The organic photoelectric conversion elements obtained in Examples 1 to 3 and Reference Example 1 were subjected to a heat resistance test in which they were kept at a temperature of 200°C for 50 minutes, and the external quantum efficiency of each organic photoelectric conversion element after the heat resistance test was measured. The results are shown in Table 1.

[0156] [Table 1]

[0157] Table 1 shows that by using the organic semiconductor ink of the present invention and introducing a crosslinked structure with a thermosetting component, it is possible to obtain an organic photoelectric conversion element with high external quantum efficiency after a heat resistance test, i.e., a photoelectric conversion layer and an organic photoelectric conversion element with excellent heat resistance. Furthermore, it can be seen that the degree of heat resistance tends to be higher as the heating temperature during heat curing increases. This is thought to be because the higher the heating temperature, the more the epoxy resin curing reaction progresses, and the higher the degree of crosslinking, the more effectively changes in compatibility due to flow between the p-type and n-type organic semiconductors are suppressed, thereby suppressing the decrease in photoelectric conversion efficiency. Reference Example 1 uses the organic semiconductor ink of the present invention, but does not undergo heat curing, thereby simulating a photoelectric conversion layer made of a conventional organic semiconductor ink, and is therefore inferior in heat resistance. [Explanation of symbols]

[0158] 10 Organic photoelectric conversion element 11 1st electrode 12 Hole transport layer 13 Photoelectric conversion layer 14 Electron transport layer 15 2nd electrode 20 Organic photoelectric film

Claims

1. The composition contains a non-crosslinkable p-type organic semiconductor, a non-crosslinkable n-type organic semiconductor, a thermosetting component, and a solvent, the non-crosslinkable p-type organic semiconductor is a conjugated polymer containing a benzodithiophene structure and a thienothiophene structure, The non-crosslinkable n-type organic semiconductor is a compound represented by the following formula (I): An organic semiconductor ink characterized in that the thermosetting component is bisphenol A diglycidyl ether. 【Chemical Formula 1】 (In the above formula (I), A represents an atom selected from Group 14 of the periodic table; X 1 to X 4 each independently represent a hydrogen atom or a halogen atom; R 1a and R 1b each independently represent a linear or branched alkyl group; and R 2 to R 5 each independently represent a linear or branched alkyl group, a linear or branched alkoxy group, a linear or branched thioalkyl group, or a hydrogen atom.)

2. The organic semiconductor ink of claim 1 , wherein the thermally curable component further comprises a curing agent.

3. 3. The organic semiconductor ink according to claim 1, wherein the epoxy equivalent of the bisphenol A diglycidyl ether is 50 to 1000 g / eq.

4. 4. The organic semiconductor ink according to claim 2, wherein the content of the bisphenol A diglycidyl ether in the thermosetting component is 38 to 100% by mass.

5. 5. The organic semiconductor ink according to claim 1, wherein the curing temperature of the thermosetting component is in the range of 100 to 220°C.

6. 6. The organic semiconductor ink according to claim 1, wherein the content of the thermosetting component is 1 to 100 parts by mass relative to a total of 100 parts by mass of the non-crosslinkable p-type organic semiconductor and the non-crosslinkable n-type organic semiconductor.

7. 7. The organic semiconductor ink according to claim 1, wherein the solid content is 10 to 30 mg / mL.

8. 8. The organic semiconductor ink according to claim 1, wherein the solvent comprises an aromatic solvent.

9. 9. The organic semiconductor ink according to claim 1, wherein the non-crosslinkable p-type organic semiconductor is a compound represented by the following formula (II): 【Chemistry 3】 (In the above formula (II), n is a positive number.)

10. A photoelectric conversion layer obtained by heat-curing a coating of the organic semiconductor ink according to any one of claims 1 to 9.

11. An organic photoelectric conversion element comprising the photoelectric conversion layer according to claim 10 .

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